Differential tensiometer



7 May 26, 1953 ALLEN 2,639,612

DIFFERENTIAL TENSIOMETER Filed May 29, 1947 3 Sheets-Sheet l FIG. I.

HERBERT ALLEN MENTOR;

May 26, 1953 H. ALLEN 2,639,612

' DIFFERENTIAL TENSIOMETER Filed May 29, 1947 3 Sheets-Sheet 3 HERBERT ALLEN INVENTOR.

BY v I Patented May 26, 1953 DIFFERENTIAL TENSIOMETER Herbert Allen, Houston, Tex; assignor to Cameron Iron Works, Houston, Tex., a. corporation of Texas Application May 29, 1947, Serial No. 751,412

4 Claims. (01. 73 -144) purpose of providing a direct reading, at the groundsurface, of the weight with which a drill bit is. hearing on the bottom of a bore hole in an earth drilling operation. It is the usual practice in Such operations to provide a tensiometer for indicating or reading directly the total weight of the drill pipe, .drill collar and drill bit suspended by the hoisting apparatus or draw works of the drilling rig. Such conventional tensiometers or weight indicators operate upon the principle of positioning an elastic member such as a spring in such a manner as to produce a predetermined deflection or a lateral displacement of a portion of the anchor cable or dead line of the draw works, coupled with an indicating mechanism for indicating. the amount that this dead line straightens out when a load is placed upon it. However, it is desirable to provide an indication or direct reading of the amount of weight with which the bit is allowed to bear on the bottom of the bore hole, and this cannot be done by the simple expedient of adjusting the pointer of a conventional indicator to a zero position on the dial after the entire weight of drill pipe, drill collar and drill bit are suspended from the draw works, because the straightening effect of a given weight increment on the dead line is different for different total Weights.

It is, therefore, a more specific object of this invention to provide a tensiometer which will i give a direct and satisfactorily accurate reading at the ground surface of the tension on a cable used to suspend a drill bit in a well thereby showing the weight with which the drill bit is bearing on the bottom of the bore hole.

A further object is to provide a structure in which there is provided a subtantially frictionless pivot for one of three misaligned abutments for a cable so that there will be reduced the errors in indicating such weight.

A further object is to provide such a'structure with means for adjusting it for use in systems withdifferent mechanical advantages in combination with means for limiting movement of the spring plate hinge providing said pivot to be within a predetermined range whereby excessive fluc 1 tua-tions of cable tension do not injure the hinge.

Other objects and advantages of this invention will become apparent from the following descrip- Q tion taken in connection with the accompanying drawings wherein is setforth by way of illustration and example but not by way of limitation, one embodiment of the invention:

In the drawings:

Fig. 1 is a front elevation of a tensiometer constructed in accordance with this invention but with the dial and pointer thereof removed and parts broken away and shown in cross section to illustrate certain of the inner mechanism;

Fig. 2: shows a cross section of the structure illustrated in Fig. 1, taken along the line 2'-2 of Fig. l;

Fig. 3 is a fragmentary cross section taken along the line 3-3 of Fig. 2 and showing one of the line or cable engaging members;

Fig. 4 is a front elevation of the instrument illustrated in Figs. 1 and 2 with the pointer and dial in place thereon; and

Fig. 5 is a fragmentary perspective showingthe fastening device whereby the pointer is secured to its hub.

The tensiometer illustrated in the drawings is adapted to be mounted on the dead line or cable I, the tension in which is'to control the operation of the instrument and be indicated on the dial thereof.

The tensiometer structure has as its basis a frame, one portion, 2, of which is made of cylindrical form to receive the dial and certain parts of the indicating mechanism as will be hereinafter described. The main portion of the frame consists of a channel formed with a web 3 which is likewise the back surface of the cylindrical portion 2, and the flanges 4 and 5 which extend rearwardly from the web 3. This channel shaped portion of the frame extends downwardly below the cylindrical part as indicated by the numeral 6. The upper end of this channel shaped portion is partially closed by means of a wall I which is notched at 8 to receive a portion of the cable I which in turn passes longitudinally through the channel shaped part of the frame.

' Extending between the flanges l and 5 adjacent their upper ends and just below the notch 8 is a cable or lin engagin member in the form of a roller 91 mounted on a pin or a shaft Hi which extends between the webs 4 and 5 and is fixedly secure thereto.

thickened portion H as shown at M and has a pair of spaced flanges extending rearwardly from each of its edges as. shown at IE to provide a. short channel shaped section with the shaft 16 carried between the flanges I5. Rotatably 3 mounted on the shaft I6 is a line engaging member in the form of a roller [1. Due to the flexibility of the element l3 the line engaging member l! is movable with respect to the frame so that it may moved to engageand deflect laterally apar tibuilar portion of the cable- 1; and so that it may be moved by straightening of the cable as a load is placed thereon. k

The web like lower extension I4 is provided with a riveted-in or otherwise secures guide member or dowel I8 adaptedto receive one end of the spring or other le r'nht it by which the movable line engaging member Il may be urged into such position as to deflect laterally a portion of the line. it is to be noted that while the element l9 has been referred to as an elastic member, this element need not take the exact form illustrated but may be any suitati w'ell known form of device which will be yieldable under increases and proportionately decreases in loads imposed ter'infelas cf as herein used -l'n 'e a ev T ppposite end of the spring 19 or the like i 2 W :95: wan ed @01 n. bilimifnt or anchor 'Ihisfi'noiint'in'g in the present instaha is illustrated having a heme, p jenon *2 I extending into and serving as a game Qr. 9i fil. ieia niee in. ss e t .1: airmen is hreaded to ca =.e rriedn t e .1 this graham ing i urnse red to the name by dreams of screws 2 or the like. The stem is i. ?e .ent. lie mat i wire-rely with i e'sp'eetfto the moun in plate '23 by means 6r a it formed integral with the stem. The stern is adapted to be rotated by iifea'ns of a handlefztfiipon its outer end.

willbie en that by rotationof theha'hdle fie thawing fitness-ring is wl'iichfisfmost eriiote from the line engaging'element i1 may "be adjnsted toward and away from the line "e'ngag-fir; names; "so as to apply a "force {to the line "engaging "element and adjust the position (if the if gingeileinentfto an arbitrarily'selected "reposition. by adjustment 'bfth'e hanare it is jidsb'ibl. with any givenl'da'd on'the or table l, 'to 'incve the line engaging "elefl"? any arbitrarily selected predeteniiiiiea zero osruen, thereby producing is'andard 'initial"deflection or the'cable 1 withdiit e'f'g'ara to the anteater im'tiaftension in the f hI 1 :11 "order to limit the movement or 'thetowelptirtion {6 1" fuife flexib e mem er r3 which is or relatively -we'ak construction as eiapai-ea 'with the spring [3, and thus prevent its injui'yfd'ue to excessive v movement, there is provided a bolt :screw fi threadedly'engag'ing the frame at 28 andlgcked in-place. in such threaded engagen ent by a :nut 29. This bolt 'is positioned so 2.. i esifen l r s a ii 'n n 5111 h flexible member l3 and the had 3l pr'th Ibo-1t siim is nqvaee w i fi ai m be t ;le ft-as;the Sq-13 18 is seen in Fig. 2 df thejdrawings jwhe reas thetwo nuts 32 which are locked together in suitably adjusted position ion the screw '2] serveas a stop to prevent excessive e rese it e erof ihe- X e-m m- *ber l3 to the' right as the same is seen in Fig.2. -Between the-point at which the spring 1-9 and $12 1? i e en a i g. mb r H re un On e g iflgxible member l3,- and the'portion e f-this member which is secured to the frame portion H,

this member I3 has formed integral with it a laterally extending part 33 and this part 33 is joined to the lower portion M by means of webs 3d, thereby insuring that substantially all of the flexing of the member [3 will take place between the lower end of the thickened section II of the frame and the laterally extending arm 33. Thus, as the line engaging member [1 is moved to the left or the right as seen in Fig. 2, the laterally extending. arm 33 will be moved upwardly or downwardly in direct proportion to the movement of the iii-smear n.

A post 35 has its lower end portion extending through an opening in the arm 33 and secured therein by means of nuts 36. This post passes upwardly through an opening 31 in the frame in to the cylindrical portion 2 of the frame heretofore referred to. At its upper end this post 3&3 also passes through an opening 38 in the base portion '39 'of a flexible indicator element havfour substantially upstanding parallel hexi'ble megs 40, M, M and '43 respectively. The legs 42 and 43 are joined together by a section M into which the post 35 is threadedly received. The legs 40 and 12 are provided by substantially bi'furcating an upwardly extending arm #5 integral therewith, and likewise the flexible legs M and 43 are provided by a. substantial bifurcation of an upwardly extending arm d5 integral therewith. It will be seen that an upward moveinent of the post 35 will prodnce a swinging mover'nent of the 35 and 46 so that their upper ends will move away from each other whereas downward movement of the post 35 will cause the upper ends of the arms 45 and 45 to move toward each other.

Pivoted in an adjusted position as at 4? to the upper e'nd of the 46 is a link 18. A swinging lever is pivoted at $9 to the upper end of the arm '45. The link =48 is pivoted-in an ad- 'justed position as at '50 to the lever cau'ied by the arm 45 and the lower end of this 'le-ver is formed with a segmental gear 51 in meshing engagement with a pinion 52 inoun'ted "on a short shaft '53. This shaft '53 is icarried inxa bearing in the arm '45 and in a second bearing in the t-racket 54 secured by means of screws '55 to the arm45.

one end of the shaft 53 extends toward the front of the structure in the open side *of the cylindrical portion 2 of "the frame "and received on this end and keyed thereto is a disc "56 having a hub- 51. Referring to 1 5 itwill "be seen that on the outer end of this hiib 5! is formed an ewngaceaiug 5 8 having an over-hanging end "portion 59 leaving between it and the end of the lug aspace =60. The pointer =6 is'tforin'ed with a slot therein adapted to receive thelug 58 and be held in place by the overhanging portion 59 thereof. The slot *in the pointer 6! is'o'f -a length I onlyslig'htly i greater than'the -nkinundercii t portion of the lug fit. The pointer SlIflbeing made of a spring like material, rnust 'bebeht to enter the space 60 and wheh 'fully engaged "with the space "60 the opposite end "of the slotnrillsnap The disc 56 is made'of 'afsiiitable'nietal or other "el'ectric alconductor"and aiha'rtof its circumference is disposed b'etweenth'e'poles'of a permanent magnet 62 which is "secured by "means of "s'crews'53 to the frame.

In substantially the same plane as ithepoin'ter of an annular member 64 having suitable indicia formed thereon as shown in Fig. 4. This dial is prevented from rotation with respect to the frame by means of screws 65 which secure it to the permanent magnet 62. The outer periphery of the dial is carried in the countersink 66, together with a ring 61 having internal gear teeth thereon throughout at least a portion of its inner periphery, and having a pointer 68 thereon extending inwardly from the ring at a suitable location. This pointer 68 may be of transparent or translucent material so that the markings on the dial 64 will show through it, or it may have an opening therein so that the numerals on the dial 64 may be seen through the pointer if the pointer is of opaque material.

The internal gear'teeth on the ring Bl are engaged by a pinion 69 on the inner end of a short shaft 10, the outer end of which carries. a knob II by which the shaft may be rotated. A suitable transparent cover such as glass I2 may be disposed over the open end of the cylindrical portion 2 of the frame and held in place by a suitable ring I3 secured to the frame by screws I4. The shaft I is provided with a bearing carried by the ring I3 so that upon rotation of the knob 11 the ring 61 carrying the pointer 68 may be adjusted to any desired position.

It is to be noted furthermore that the pointer 68 may be made ofa distinctive color so as to readily catch the eye and this color may if desired be the color of the pointer 6 I. v I

The cable I, intermediate the line engaging members 9 and I1, is engaged by a block I having a notch 16 to receive the cable. This block '15 may be disposed either directly against the flexible member I3 or suitable shims 'I'! may be placed between them to adjust the position of the cable I with respect to the frame so that variations in the mechanical advantage of the load exerted on the cable will be compensated for. In the case of a drilling rig for drilling wells, the mechanical advantage to be compensated for is determined by the number of lines between the crown block and the travelling block.

The shims in such case will preferably each be of such thickness that moving one shim from the position IT to the position 80 will compensate for the addition of two lines between the crown and travelling block, and vice versa. The cable is held-against the block I5 by means of block I8 likewise having a notch I9 to receive the cable. The two notches I6 and I9 are preferably shallow enough so that the two blocks I5 and I8 cannot be brought entirely together with the cablebetween them. Shims 80 may if desired be placed onthe outer surface of the block 18.

The flexible element I3 and the thickened portion II of the frame are provided with a channel BI adapted to receive the U-bolt 82 that passes outwardly through suitable openings in the blocks and'l'8 and has its projecting ends engaged by suitable nuts 83. The nuts 83 when tightened will serve to clamp the cable I between the blocks I8 and 15 and to clamp the block I5 tightly against the flexible element I3. It will be seen that the positioning of the shims I1 and 80 will determine the exact location of this central portion of the cable, but that once clamped, this portion of the cable and the block I5 which forms a line engaging member will be fixed with respect to the frame.

In operation, a suitable deflection of the cable I by the line engaging member I'I will cause the pointer 6| to be positioned-on the zero mark of the dial 64. After the entire weight of drill pipe, drill collar and drill bit to be employed in the drilling operation has been suspended by the draw works of which the cablel forms a part, the cable will have straightened out somewhat and .the pointer will indicate a position other than zero on the dial. Then the handle 26 will be turned to adjust the position of the end of the spring I9 which is nearest the frame until this spring bears the line engaging member I! outwardly a sufficient amount to move the pointer 6| back to thezero mark on the dial. At this point the deflection of the cable or line will stand at the original arbitrarily selected zero position. Then if it be desired to place say 10,000 pounds of weight on the bottom of the hole by contact of the drill therewith, the draw works will be slacked off until the pointer 6| indicates 10,000 pounds on the'dial 64. Inorder to enable the driller more readily to keep the pointer 6| at this point, the knob 'i'l may be rotated until the pointer 88 coincides with the 10,000 pound mark on the dial. I Thereupon the driller will begin his drilling operation easing off or takingup on the draw works as necessary to maintain the pointer BI coincident with the pointer 68. As long as this is done, he will be sure with reasonable degree of accuracy of maintaining the desired10,000 pounds of weight on the bottom of the hole. The weightto be maintained on the bottom of the hole will be selected by the driller with a view to causing the drill bit to drill most efficiently in the formation which happens to exist at the bottom of the hole.

Now let it be assumed that the drilling has continued until it becomes necessary to add at the upper end of the drill stem an additional section of drill pipe. The additional section is screwed on to the upper end of the drill stem and then the entire drill stem including the added section of drill pipe will be suspended from the draw works. Naturally since added weight is suspended, the pointer 6| will swing from zero in a direction opposite that in which it moved from zero when weight was slacked off on the bottom of the well, and will swing an amount corresponding to the weight of the added section of pipe. The handle 26 will then be adjusted so as to move the cable deflector which includes the line engaging member I? back to the original arbitrarily selected zero point, after which the pointer GI will again register zero on the dial 64. Thereupon weight is slacked off until the pointer 5| coincides with the pointer 68 and drilling again proceeds as before.

It will be seen that inasmuch as the zero point is always set with the full weight of the drill pipe on the cable, the deflection of the pointer 6| will always indicate the weight on the bottom of the hole. Furthermore, it will be seen that since when the pointerGI is at zeroon the dial, there is always the same amount of deflection on the cable I regardlessof the weight suspended by the cable, meaurement of the weight placed on the bottom of the hole will start from the same arbitrarily selected deflection ofthe cable regardless of the weight of the drill stem. The only part of i the device which will have a difierent zero status for each initial weight-is the spring I9 or its equivalent. Since this spring I9 has a straight line load deformation characteristic, the amount of its deformation for any zero setting will not affect the accuracy of theinstrument in indicating increases. or decreases from the zero setting.

Hence I errors .which. would be introduced if the measurementbegan with the cable less deflected at sometimes than at others, will be substantially eliminated.

It will be appreciated that while one of the principal uses of this device is in determining the amount of weight on the bottom of the hole during drilling, it will likewise be useful in determining the amount of pull exerted upon .a stuck bit in an effort to release it, and .for numerous other purposes in connection with drilling wells. Furthermore, it will be found useful in any location wherein it is desired to indicate or read directly the amountof variation in tension upon a flexible line as disti uished from the total tension thereon.

Having described my invention, I claim:

1. A load indicator particularly adapted to measure changes in the tension of tool support ing cables in the drilling of a well which com-- prises, in combination, a rigid frame, a first abutment carried by the frame, a second abutment carried by said frame and spaced from said first abutment and including a releasable clamp adapted to irict-ionally engage ,a cable so as to support the indicator thereon, a third abutment spaced from the first and second abutments and out of alignment therewith so that when a cable is brought into engagement with all three abutments-and-clamped :by said clamp a portion of the cable ,is deflected laterallma flexible-spring plate hinge having one of its ends fixed to the frame and its-other endextending from the frame, said third abutment being mounted on saidother end of the hinge, the hinge being stiiiened along a major part of its length remote from the frame to prevent bending-of saidpart, a spring between the frame and. said other endof the plate urging the third abutment into misalignment w th the first and second abutment's, means for adjusting the urging force of said spring, stop parts carried by the frame, one .on each ,side of said other end of the plate, limiting movement of the other end of the plate to be within a predetermined amount so that the plate hinge is protected from excessive fluctuations in cabletension, an indicating means carried by saidliiiamelandconnecting means between said indicating means and said'other' of the flexible plate whereby movement of the flexible plate is transmitted to said ind'ild jifi means.

2 The combination of claim .1- wherein said spring between the frame and the other end of said flexible plate haslstraightline characteristics vwl'lereby, upon attachmentlofthe indicator to a cable under tension, the spring can be adjusted to position said other end of thetplate hingeat a position between said ston'pa-rts andagiven change in cable tension willvresul't in apnedetermined extent ofv plate hinge movement irrespective of the initialoab'le tension 3. In a line load variation indicator. of the type having a substantially rigid frame having three spaced abutments thereon adapted to: receive a line the-loadiuponwhich-is to be measured; said-abutmentsrbeing,outzof alignmentgwitheach other .so that wh'en:.,a=. 1line ;is brought into engagement witlnallzthree ,abutments aportion of' the: line:' will be deflected laterally the improvement which; resides- ;in the: combination therewith: or. an adjustable mounting; for one: of.

the. abu'tments including. anrelastic; system inf-sing the: adjnstably mounted abutment-in: adirection to maintain the abutments:inmisalignment said remaining por ion t reof exte din fro s id frame for carrying the adjustably meunted abut,- merit, said remaining portion being stiffened along a major part of its length remote from said frame to prevent bending of such part, thereby providing an anti-friction flexible plate hinge between said stiffened part of said plate and said creme, a rigid arm connected rigidly to the stiffened portion of the spring plate and extending therefrom so as to be rotatable about the flexible portion of the spring plate, a force transmitting post rlgidly connected to said arm and extending sub tantially parallel to said s ring plate whereby movement of the adjustably mounted abutment is transmitted in a direction substantially parallel to said spring plate, and an indicator means connected to and responsive to movement of said force transmitting post.

4. Ina line load variation indicator of the type havin a substantially rigid iraz'ne having three spaced abutments thereon adapted to receive a line the load upon which is to be measured, said abiltrn'ents being out of alignment with each other so that when a line is brought into engagement with all three abutments a portion of the line will be deflected laterally, the im rovement which resides in the combination therewith f an adjustable mounting for one of the abiit'innts including an elastic system including a flexible spring plate with one end ri idivseeured to the frame and with the remaining portion thereof extending from said frame for carrying the adjustably mounted abutment, said remaining portion being stiffened along a major part of its length remote from said frame to prevent bending of such part and to provide a flexible plate hinge between saidstiffened partof said plate and said frame and an adjustable elastic member carried between said frame and said sitifiened part of said plate to urge theadjtvstable abutment intoinisal'ignment with the other abutments whereby said elastic member can be adjusted to move said adjustable abutment to the same location when the line load is changed, a rigid arm connected rigidly to th s'tiiiened portion of the spring plate and extendin therefrom so as to be rotatable about the flexible portion of thespring plate, a force transmitting post rigidly connected to said arm and extending parallel to said spring plate whereby movement of the adjustably mounted abutment is transmitted in adire'etion substantially parallel to said spring plat'e and an indicator means connected to' and responsive to the position of said force transmittingpos't.

HERBERT ALLEN.

References Cited in the 'file" of this patent UNITED STATES 

